If configure finds that inet_aton() is not present on this platform,

If configure finds that inet_aton() is not present on this platform,
include the version from backend/port into libpq.
There is a second-rate implementation of inet_aton() already present
in fe-connect.c, #ifdef'd WIN32.  That ought to be removed in favor
of using the better version from port/.  However, since I'm not in a
position to test the WIN32 code, I will leave well enough alone for
this release...